Multimedia communication requires the simultaneous delivery of time synchronized voice, video and data signals. A Multimedia Access Network has the task of delivering such signals to and from a switching entity and the multiple subscriber premises which it services. The switching entity acts as a gateway to the rest of the world and allows the subscribers access to the multiple backbone networks terminating on it. For this reason the switching entity can be called an Access Gateway (AGW). At the subscriber's premises, a Residential Gateway (RGW) terminates the multimedia signals from the switching entity AGW and regenerates the communication services being consumed at the premises.
U.S. patent application Ser. No. 08/269,370 filed Jun. 30, 1994, now U.S. Pat. No. 5,555,244 and entitled "Scalable Multimedia Network" (incorporated herein in its entirety by reference), is concerned with many of the problems associated with the suitability of multimedia communication services on an AGW.
The AGW must communicate with the RGW over some type of physical media. This media may be wireless or wireline. Multimedia wireless communication is a topic undergoing much research and is an emerging technology. The most common wireline media currently deployed uses Hybrid Fiber Coax (HFC) drops for broadcast video services and twisted pair copper drops for Plain Old Telephone Service (POTS).
HFC drop networks are being deployed by CATV operators and have an advantage in that they are based on broadband physical media. However, HFC networks are deployed as shared media whereby hundreds (even thousands) of subscribers tap onto one run of cable. Such an architecture is highly cost-effective for downstream broadcast services, but creates a difficult multiple access problem when the RGWs at the subscriber try to communicate upstream with the AGW.
Current, or second generation, so-called Fiber-To-The-Curb (FTTC) access networks are being deployed by access network providers to deliver broadband services. In such FTTC networks, optical fibers connect the AGW to multiple Optical Network Units (ONUs) located in the outside plant. From each ONU, coaxial cable and pre-existing copper pairs are used to provide POTS and broadband services to the subscriber. Such ONUs provide broadband distribution, but because they are essentially multiplexing entities and not switches, they typically can serve only a limited number (e.g., 16 to 32) of subscribers and therefore, are difficult to justify economically.
Virtual circuit switches, generally ATM-based, are being deployed for the AGW function. However, the per port cost of a virtual circuit switch today does not justify dedicating a port to each subscriber, and therefore, virtual circuit switching functionality is not found typically located in the access network near subscribers.
Multimedia services tend to be asymmetrical, i.e., the "downstream" services to subscribers require greater bandwidth than the "upstream" services from subscribers. Because the downstream services also tend to be broadcast or multicast, providing a port per subscriber on a virtual circuit switch is expensive and wasteful of scarce network resources.
A need exists for a FTTC architecture that can allow access network providers to offer broadband services to a large number of users economically.